Very minor things:
- A few renames
- Instead of having two constructors call a third constructor, just have one constructor call the other.
- Invoke FFT with the option that specifies the inputs are mostly zero, as a (minor) optimization
- Remove unused field
Mainly storing pending generators in a Vec rather than a HashMap. Requires an extra check to make sure we don't run one twice after adding it to the Vec twice.
* Add a tree of scopes for proving times
To replace the old `timed!` macro, which had no hierarchy.
It's similar to `ContextTree`, which tracks gate counts of circuit operations.
This gives a more organized output, with indentation levels based on scope depth, parent durations listed before child durations, etc.
* PR feedback
No functional changes here. The biggest change was moving certain files into new directories like `plonk` and `iop` (for things like `Challenger` that could be used in STARKs or other IOPs). I also split a few files, renames, etc, but again nothing functional, so I don't think a careful review is necessary (just a sanity check).
